Recommendation 6 of the 19th CCTF (2012)

A contribution from the Consultative Committee on Time and Frequency (CCTF) on achieving a continuous reference time scale

The CCTF, having analyzed the terms of WRC-12 Resolution 653 adopted by the World Radiocommunication Conference (WRC) 2012 on the Future of Coordinated Universal Time (UTC) which invites the ITU WRC 2015 to

“consider the feasibility of achieving a continuous reference time-scale, whether by the modification of UTC or some other method and take appropriate action, taking into account ITU-R studies,”

and instructs the ITU Secretary-General

“to bring this Resolution to the attention of relevant organizations such … the General Conference on Weights and Measures (CGPM), the Consultative Committee for Time and Frequency (CCTF), the Bureau International des Poids et Mesures (BIPM) …”

Recommends that the following facts be recognized in the implementation of a continuous time scale:

1. a continuous time scale is indeed achievable, and that it has been realized and maintained by the International Bureau of Weights and Measures;
2. a continuous reference time scale corresponds to UTC without leap second discontinuities;
3. the concepts of continuity and uniformity should be applied strictly in a reference time scale;
4. the unit for any quantity in metrology is unique, and as such, a single time scale should also be unique;
5. in the event of a redefinition of any quantity in metrology, the unit should be invariant, and particularly for the second of the Système International the respective scale should be continuous and uniform;
6. the name “Coordinated Universal Time” be maintained in the case of a redefinition of UTC without leap second adjustments;
7. the term “Universal” in “Coordinated Universal Time” implies that the time scale is to be used throughout the world;
8. the term “Coordinated” in “Coordinated Universal Time” implies coordination among National Metrology Institutes and not a relationship to the direction of the Sun from a position on the surface of the Earth;
9. the angle UT1 used to relate celestial and terrestrial reference systems should not be considered as a time scale, but as the angle that characterizes the variable rotation of the Earth;
10. the International Earth Rotation and Reference Systems Service (IERS) provides a means of accessing UT1 in real-time by means of routinely available predictions of UT1-UTC with precision 100 000 times better that the coarse approximation UT1 = UTC currently provided by means of coding UTC to match UT1 within 0.9 second;
11. a wider dissemination of UT1-UTC is to be encouraged;

and further recommends

that the International Committee for Weights and Measures (CIPM) and the International Telecommunication Union – Radiocommunication Sector (ITU-R) consider the formation of a joint working group to study the possibility of coordinating future actions in the definition of the continuous world-reference time scale.

DOI : 10.59161/CCTF2012REC6E